Method for producing nitrogen from internal-combustion engine exhaust gases



E. L. PRIDoNoFF ErAL. 2,409,386 Y METHOD FOR PRODUCING NITROGEN FROM INTERNALCOMBUSTION` ENGINE EXHAUST GASES Fi1ed June 30, 1944 2 Sheets-Sheet l amwwwwi mmm wm @o5 .NNWT vu OCL l5, 1946- E. L. PRlDoNoFF TAL `2,409,386

METHOD FOR PRODUCING NITROGEN FROM INTERNAL-COMBUSTION V ENGINE EXHAUST GASES Filed June 50, 1944 2 Sheets-,Sheet 2 PJ" EIL- los , 0'5- f /l/ g /07 -v 26 /04 ,L l 36 l 34 'l /08 a., f /08 v y ./o/ /o0 lo, o /oo INVENTORS Een: L. PRIDONOFF A/THUR J. SOHNE/DER v Patented Oct.- 15, 1946 METHOD FOR PRODUCIN G NITROGEN FROM INTERNAL-COMBUSTION ENGINE EX- VHAUST GASES Eric L. Pridonoff, Alhambra, and Arthur J.

Schneider, Pasadena, Calif., assignors to Aerojet Engineering Corporation, Azusa, Calif., a

corporation of Delaware Application June 30, 1944, Serial No. 543,042

2 Claims. l

This invention relates to inert gas generators and has for its object to produce an inert gas under high pressure.

Inert gases such as nitrogen compressed in suitable tanks are useful for supplying gas pressures. According to our invention we provide a system for producing such an inert gas under relatively high pressure, such as 2500 pounds per square inch. The system comprises an internal combustion engine, for example, a gasoline engine which burns gasoline and air. The exhaust gases of such an engine contain the nitrogen from the air together with products of combustion such as water vapor and carbon compounds. Diliiculty has heretofore been experienced in producing nitrogen from an engine exhaust at such high pressure due to the corrosive effect of impurities and moisture in the gas. We have removed these impurities other than the inert nitrogen by sending the gases through a system of purifiers and dehydrators associated with a compressing system so that the gases are made suiciently d ry and pure to provide ecient production of the substantially pure nitrogen. In this way we have succeeded in removing the presence of undesirable components which might interfere with the operation by producing corrosive effects.

A feature of our invention resides in the novel arrangement for driving the compressors from the engine itself. Other features relate to the use of refrigerating coolers for producing dehydration and a related feature is the use oi a dehydrator for dehydrating the gases prior to their being brought to the ultimate high pressure. A related feature is the use of a purier comprising activated carbon.

Our invention will be better understood from the following description and accompanying sheet of drawings in which:

Fig. 1 is a schematic plan view of t a complete field plant;

Fig. 2 is a perspective view of the unit with panels in raised position;

Fig. 3 is a perspective view vertical panels dropped. p V

Similar numerals refer to similar parts in the drawings.

The engine l is an internal combustion engine, for example, of the type burning a vaporized hydrocarbon such as gasoline in air. VThe engine drives the multistage compressor 2 and is operated with a rather rich mixture to obtain an exhaust gas having a low content of corrosive agents. A suicient pressure is maintained by the engine to force the exhaust gases through the various conduits and installations between the engine and the compressor.

Passing these gases through a conduit 3 into the steam boiler I in which their temperature is of the unit with considerably reduced by giving up a percentage of their heat, producing steam in the coils of the bollen The gas then is discharged through conduit 8 into the gas reheater 9 at a temperature which may for example be around 500 F.

In this reheater 9 the hot gases lose an additional amount of heat and their temperature drops somewhat, say to 472 F. approx. The gases then pass through the exhaust gas cooling coil I0 and in doing this their temperature is lowered to approximately 150 F. which varies according to the temperature of the surrounding atmosphere. The above exhaust gas cooling coil I0, reheater 9 and steam boiler 'I are cooled by a steady now of air which is delivered by the blower Il.

The greatly cooled gas is led through conduit I2 into the refrigerated low pressure drier l5. The temperature of the dried exhaust gas drops to approximately which is raised to about 105 by reheating these gases in the inert gas reheater S. Conduit I6 leads the reheated gases into the charcoal chamber I8. A second charcoalchamber I9 is provided which enables the operator to reactivate one of the charcoal chambers while operating the other charcoal chamber. Such reactivation is performed by permitting steam as generated in the steam boiler 1 to wash out the impurities removed from the exhaust gases. The charcoal chamber containing a bed of activated carbon absorbs a large part of the nitric oxides, hydrocarbons and small traces of carbon dioxide present in the exhaust gases.

Since further drying of the exhaust gases is more easily and effectively accomplished by raising their pressure, these gases are now led through conduit 20 and an oil bath filter 20A into the low pressure cylinder 2| of the multistage gas compressor 2.

Thereupon the gas passes through an intercooler 22 into the second stage cylinder 23 where its pressure is raised to 200 pounds per square inch. The pressurized exhaust gas leaves the second stage cylinder 23 enteringanother intercooler 20 and hows through the inlet conduit 25 into the refrigerated high pressure dryer 26. The temperature of the gas is reduced to 45 F. in the refrigerated high pressure dryer 2G condensing some more of the remaining water vapors, which are removed by the water trap 28 inserted into the outlet conduit 2. For nal dehydration the gases are directed through conduit 2l into the silica gel chamber 29 in which their water content is further reduced to approximatelyv .01%. For the iinal pressurizaticn the gas now flows through conduit `.til into the third stage cylinder 3| of the multiple stage gas compressor 2 and is forced through a third intercooler 32 into the fourth stage cylinder 33. The gas having a pressure say of 3000 pounds per square inch leaves the fourth stage cylinder 3.3 and enters an aftercooler 39 in which its temperature is reduced to around 125 F., it being understood that the fluctuations of the gas temperatures are caused by the compression of the gases. The fully compressed gases are now led through conduit 35, gas filter 39 and gas conduit 31 into the gas receptacles 33 where they remain stored. An outlet conduit 39 leads the inert gas under high pressure to the lling nozzle 41|A which is attached to the above conduit 39.

In this system of producing an inert gas from the exhaust gases of an internal combustion engine the above cooling may be elfectuated by the insertion of a refrigerating system based on Freon as` refrigerant. Such refrigerating system comprises a refrigerant compressor 45 which raises the pressure of Freon to between 90 and 120 pounds per square inch and the temperature to approximately 95 F. depending upon external air temperature. If the pressure in the discharge line 95 between the refrigerant compressor 45 and the air-cooled Freon condenser 99 exceeds 195 pounds per square inch the relief valve 9B ventsv the excess pressure of the discharge line into the suction line 69. A discharge gage 91 indicating the pressure from the compressor is inserted between the said compressor and the relief valve 99.

The vaporized Freon is cooled to 85 F. in the Freon air-cooled refrigerant condenser 99. The Freon ows as a liquid into the refrigerant receiver 59. The liquid Freon passes from receiver 59V through conduit 5|, to a T 54 which divides the stream of Freon into two branches.

One branch directing the Freon into the thermal expansion valve 55, the other branch carrying it to the expansion valve 55. The Freon is evaporated in the valve 59 and passes through coil l thereby cooling the exhaust gases as previously stated. Expansion valve 55 permits evaporation of Freon which is led through coil 53 thereby eilectuating the cooling of the exhaust gases in the refrigerated high pressure dryer 29.

The evaporated Freon is now led into the suction conduit 99 of the refrigeration compressor 45. An evaporator pressure regulator 6| is inserted in line 69 and maintains a predetermined evaporator pressure of 25.5 pounds per square inch in the line between the expansion valves 5 5 and 5 6 respectively and the evaporator pressure regulator, regardless of sudden load changes and fluctuations in suction pressure. This pressure determines the boiling temperature of the Freon and thereby the temperature of the coils in the refrigerated low pressure and high pressure dryers is maintained at 32 F. by the evaporator pressure regulator. This is a pilot-operated piston valve maintaining a set pressure by a pilot adjustment means.

A steam system is incorporated in the system for producing an inert gas from the exhaust gases of a gasoline engine and is used to reactivate the bed of activated carbon in the charcoal chamber i9 and |9.

The steam system operates with a gear-type boiler feed water pump I9 which meters the feed water to the steam boiler through conduit 1| at pressures up to 30 pounds per square inch.

Steam is generated by continuously passing gallons per hour of water through the steam boiler 'i which is located in the exhaust gas conduit 3 and the heat of the exhaust gases boil the water to produce steam at 300 F. which consequently cools the exhaust gases proportionately. 75 tal Soft water for the boilerv may be derived from a water softener or other source.

The Water flows from the water softener tank (not shown) through conduit into the steamboiler `|l in which it is vaporized and the steam iiows through conduit TI into the steam separator T8. Excess moisture in the steam is trapped by the steam condensate separator i9 and is drained to the atmosphere.

Before the steam reaches either activated charcoal chamber |9 or I9 there is a pressure gage 8| and a relief valve `92 installed in the conduit 99. The steam flows for example into the charcoal chamber I8 below the carbon bed through valve 92. Partial condensation occurs when the steam strikes the cold metal members of the chamber. The steam removes the impurities collected by the carbon bed from` the exhaust gas which are liberated by the high temperature'of the steam and the condensate is drained out of the conical bottom of the chamber through the steam trap 84 after flowing through the strainer 83. rl'he strainer 83 prevents any foreign particles to flow into the steam trap 84 which may be damaged thereby.

Conduit 8 5 leads the steam into the second charcoal chamber |9 through valve 93 thereby permitting alternate use of either chamber during the operation of the inert gas generator. Drain outlets 96 and 81 respectively may be shut off separately by the inserted valves 88 and 99 respectively. Pressure relief valves 90 and 9| are installed on chambers I8 and |9 respectively. The steam pressure of these chambers is thereby regulated and the relief valves will blow off when such pressure reaches 30 pounds per square inch. Each chamber has, an inlet valve 92 respectively 93, which may be opened alternately for operating each chamber independently from the other chamber.

All of the above units are mounted on a frame comprising four gas receptacles 33 made of double extra strong steel pipe and having heavy head plates welded into their several ends. These tanks are Welded in pairs to the flanges of two channels |95 (Fig` 2,) which are placed parallel to each other at a distance and are curved upward at each end,` facilitating their use as skids for the entire generator. Diagonal cross members secure the proper spacing of the tanks 38 and channels |99. A steel plate |92 is welded between the channels and a bit above the channel web covering the entire bottom of the frame and is curved upward in a manner which is similar to that of 55 the two channels |99, thereby providing a dirtproof frame bottom whichy may act as a secondary skid and support. An angle iron framer |93 with cross members is welded to the top of the gas tanks 39. The outside gas receptacles 39a and 38h are provided with drain valves S45 and 99 (Eig. l) respectively.

A plurality of posts |99 are welded to the angle iron frame |93 supporting a roof |95. The roof is made of angle iron with channel cross members having a sheet iron plate welded thereto. An ample opening is provided in the roof above the exhaust gas cooling coil I9 which may be closed by a hinged door |96.

The entire sides formed by the plurality of posts are enclosed by a plurality 0f panels |91 consisting of sheet iron welded over an angle iron frame and enclosing a thickness of insulating material. The vertical panels |91 are hinged at their top to the angle irons of the roof frame, except the horizonpanel which is second from thev front on the right side and is hinged on one side (not shown). When the generator unit is to be used each panel is swung upward and is supported in a horizontal position by two poles |08 which are hinged to the inside bottom of the panel. The support poles |08 are secured at the top inside of the panel when not in use.

A standard steel pipe |09 is welded between the flanges at each curved end of the two channels providing towing bars. A part ofthe channel web being removed to facilitate easier access to the towing bars.

For the purpose of lifting the generator unit, cable guides I|0 respectively (Fig. 3) are welded to the outside of the channels at each end, and to the edge of the roof on both longitudinal sides near the center of the unit, to guide the cables when the unit is lifted.

When gasoline and air have been used in the engine, a chemical analysis of the purified compressed inert gas has shown the following composition, the proportions being percentages by weight:

Per cent Nitrogen (N2) 86 Carbon dioxide (CO2) 12.5 Water (H2O) .01 Carbon monoxide (CO) 1.1

Oxygen (O2) .2

Per cent Nitrogen (N2) 98.4 Carbon dioxide (CO2) .01 Water (H2O) .01 Carbon monoxide (CO) 1.1 Oxygen (O) .2

For the proper operation of our generator the following steps may be followed: When starting the inert gas generator, the blower I| is started first; the boiler feed water pump is engaged next and the gasoline engine I is started after its clutch has been thrown out disengaging the multistage compressor 2. Engine may be left running for ve minutes.

After engaging the multistage compressor the bleed valve may be opened for a short time, thus relieving the discharge line 35 and the iilter 31 whereupon the bleed valve may be closed.

It takes about 45 minutes for the gas compressor to build up the gas receptacle pressure to 3000 pounds per square inch. When this pressure is reached:

l. The speed of the gasoline engine should be reduced until the production of inert gas is equal to the rate of use,'o

rs 2. Sufficient gas should be bled off through the bleeder valve 35a to prevent the pressure from rising further, or

3. The gas compressor should be stopped by disengaging the clutch. En such a case the refrigeration compressor should be stopped until the gas compressor is started again.

From the foregoing description and the attached sheets of drawings it can be seen that we have provided a positive inert gas generator useful for field operation.

By reason of the use of the activated carbon chambers I8 and I9 substances which have been especially harmful in producing corrosive effects, particularly the oxides of nitrogen, are removed. Since even small traces of nitrogen oxides tend to produce corrosion in the presence of moisture, especially at the high pressures to which the nitrogen is ultimately raised, the subsequent eiiicient dehydration in the refrigerating coolers 51 and 53 is especially salutary. By reason of the low temperatures to which they cool thegases passing through them they separate most of the moisture from the gas. The use of the silica gel chamber 29 before the gases enter the final high compression stages of the compressors is of especial advantage in removing the last harmful traces of the water, which if present with oxides of nitrogen in the high compression stages would produce corrosion. By reason of the combination and correlation of the stages of purification, dehydration and compression in the manner disclosed herein we have produced -a simple and effective pure nitrogen generating system of sufficiently small weight and bulk to enable it to be incorporated into a single portable unit.

We claim:

1. In the production of nitrogen gas at pressures in excess of 500 pounds per square inch from the exhaust gases of an internal combustion engine containing a large proportion of nitrogen together with oxides of nitrogen and water vapor and involving the cooling of the gas to condense water vapor, the removal of the water thus condensed, the treatment of the residual gas with activated carbon to remove oxides of nitrogen, and the compression of the gas thus purified in a multiplicity of stages with cooling between stages, the improvement which comprises treating the gas in compressed state after the last cooling stage and immediately prior` to the final compression stage with silica gel to reduce its water content and thereby reduce the corrosive effect of any residual oxides of nitrogen in the gas.

2. In the production of nitrogen gas at pressures in excess of 500 pounds per square inch from the exhaust gases of an internal combustion engine containing a large proportion of nitrogen together with oxides of nitrogen and water vapor and involving the cooling of the gas to condense water vapor, the removal of the water thus condensed, the treatment of the residual gas with activated carbon to remove oxides of nitrogen, and the compression of the gas thus purified in a multiplicity of stages with cooling between stages, the improvement which comprises treating the gas in compressed state after the last cooling stage and immediately prior to the final compression stage with silica gel until its water content is less than .01%, whereby the corrosive effect of residual oxides of nitrogen in the gas is inhibited.

ERIC L. PRIDONOFF. ARTHUR J. SCHNEIDER. 

